Nanotube chemical sensor based on work function of electrodes

ABSTRACT

In one embodiment a method for sensing specific molecules is provided. The method comprises forming a nanoelement structure and forming two spaced apart electrodes in contact with the nanoelement structure, wherein at least one of the electrodes is capable of functioning as a sensing element to sense the specific molecules.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present patent application claims priority from provisionalpatent application No. 60/429,712, filed on Nov. 27, 2002, which isincorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to nanotube devices that are sensors forspecific molecules in gaseous and liquid analytes.

BACKGROUND

[0003] Nanotubes are a unique material with rich electrical and chemicalproperties and extreme mechanical strength, which makes them suitablefor wide range of applications, including sensing molecules in gaseousand liquid analytes. Nanotube-based sensors hold great promise for suchapplications as environmental and industrial monitoring, transportation,medical devices, medical/clinical diagnostics, biotechnology for drugdiscovery, agricultural and consumer markets, national security,including both homeland defense and military operations. For generalinformation regarding carbon nanotubes, their integration in sensingdevices and their principles of work, reference may be made to thefollowing U.S. Pat. Nos. 6,346,189; 6,232,706; 6,401,526; 6,528,020 andalso Franklin, et al., Appl. Phys. Lett. 79, 4571 (2001) and Zhang etal., Appl. Phys. Lett. 79, 3155 (2001), all of which are incorporatedherein for reference for all purposes.

[0004] Fluid sensors of which the inventors are aware, and which usecarbon nanotubes and nanowires as sensing elements, take advantage ofhigh surface-to-volume ratio of nanoelements (nanotubes and/ornanowires), which makes their electrical properties sensitive tosurface-adsorbed molecules. The detection scheme in these sensors isbased on chemical interactions between the surface atoms of thenanoelements, or materials attached to the surface atoms of thenanoelements, and the adsorbed molecules in gases and liquids. There area number of drawbacks associated with the above-described sensors. Onetechnique for making a hydrogen sensor includes coating a nanotube withindividual nanoparticles of palladium (Pd). In this sensor, detection isbased on charge transfer from a Pd nanoparticle, which adsorbs H₂ to thenanotube and results in lowering the nanotube conductance. The approach,however, has several shortcomings. For example, Pd nanoparticles havebeen found to be unstable due to their oxidation after exposure to H₂This results in shorter life for the sensors.

[0005] Moreover, coating nanotubes or nanowires with a thin layer of Pdnanoparticles is inherently difficult to control and scale up, as itoften leads to electrical short circuits in the device. This isparticularly the case if the sensor design calls for an array ofindividual sensors for detection of different molecules placed in closeproximity to each other.

[0006] Another disadvantage of existing nanotube/nanowire-based sensorsrelates to an inability to effectively, or at all, prevent non-specificinteraction between the nanoelement and other molecules present in thesurrounding environment. For example, a non-functionalized nanotube maybe sensitive to NO₂. A device for detection of H₂ with nanotubes coatedwith particles of Pd reacts to both H₂ and NO₂ if molecules of bothgases are simultaneously present, since parts of the nanotube arefunctionalized with Pd, and parts are not.

SUMMARY OF THE INVENTION

[0007] According to one aspect of the invention, there is provided amethod for sensing specific molecules, the method comprising forming ananoelement structure and forming two spaced apart electrodes in contactwith the nanoelement structure, wherein at least one of the electrodesis capable of functioning as a sensing element to sense the specificmolecules.

[0008] According to a second aspect of the invention, there is provideda method for sensing specific molecules, the method comprising forming ananoelement structure, and forming two electrodes in contact with thenanoelement structure, wherein the Schottky barrier defined between atleast one of the electrodes and the nanoelement structure enables theelectrode to function as a sensor for the specific molecules

[0009] According to a third aspect of the invention, there is provided adevice for sensing specific molecules, the device comprising ananostructure; and two electrodes connected by the nanostructure,wherein at least one electrode and a junction between the electrode andthe nanostructure defines a sensing element for the specific molecules.

[0010] According to a fourth aspect of the invention, a device forsensing fluids, the device comprising at least one nanoelement; a firstelectrode and a second electrode connected by the at least onenanoelement; a third gate electrode disposed between the first andsecond electrode, wherein at least one of the first and secondelectrodes and a junction between the electrode and the at least onenanoelement defines a sensing element for the specific molecules; andwherein a gate voltage applied to the third gate electrode changes theSchottky barrier at the junction.

[0011] According to a fifth aspect of the invention, there is provided afield-effect transistor device, comprising at least one nanoelement; anda first and a second electrode connected by the or each nanoelement,wherein at least one of the first and second electrodes includespalladium.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is described by way of example with reference tothe accompanying drawings, wherein:

[0013]FIG. 1 is a schematic diagram of a nanotube electronic device inaccordance with one embodiment of the invention;

[0014]FIG. 2A is a schematic top view of a substrate with unpatternedcatalyst;

[0015]FIG. 2B is a schematic top view of a substrate with patternedcatalyst;

[0016]FIG. 3A is a schematic top view of a substrate with nanotubes andpatterned metal contacts for the substrate with unpatterned catalyst;

[0017]FIG. 3B is a schematic top view of a substrate with nanotubes andpatterned metal contacts for the substrate with patterned catalyst;

[0018]FIG. 4A is a graph illustrating the response of a nanotube devicewith Pd electrodes in accordance with one embodiment of the invention;

[0019]FIG. 4B is graph illustrating the recovery time for 0.4% H₂ atdifferent operating temperatures;

[0020]FIG. 5 is a graph illustrating the response of a nanotube devicewith Au electrodes in accordance with one embodiment of the invention;

[0021]FIG. 6A is a graph illustrating sensitivity dependence ondifferent H₂ concentrations without gate voltage;

[0022]FIG. 6B is a graph illustrating sensitivity dependence ondifferent H₂ concentrations with −5 V gate voltage, the sensitivitybeing defined as conductance difference before sensing and after sensingdivided by base conductance;

[0023]FIG. 7 shows the real time current measurement with differentconcentrations of strepavidin;

[0024]FIG. 8A is an AFM (atomic force microscope) image of an electrodebefore sensing;

[0025]FIG. 8B is an AFM image of an electrode after sensing;

[0026]FIG. 9 are diagrams illustrating the sensing of streptavidin afterbiotin-immobilization; and

[0027]FIG. 10 shows a real-time current measurement when streptavidinwith different concentration was added. 333 nM strepavidin induced anobvious current decrease.

DETAILED DESCRIPTION

[0028] In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the invention. It will be apparent, however, to oneskilled in the art that the invention can be practiced without thesespecific details. In other instances, structures and devices are shownin block diagram form in order to avoid obscuring the invention.

[0029] Reference in this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention. The appearances of thephrase “in one embodiment” in various places in the specification arenot necessarily all referring to the same embodiment, nor are separateor alternative embodiments mutually exclusive of other embodiments.Moreover, various features are described which may be exhibited by someembodiments and not by others. Similarly, various requirements aredescribed which may be requirements for some embodiments but not otherembodiments.

[0030] The basic structure for a nanotube sensor is shown in FIG. 1.Each sensor includes a source electrode 11, a drain electrode 12, anoptional gate electrode 13, and at least one nanotube or a network ofnanotubes 14 connecting the source and the drain to form a field-effecttransistor, if the gate electrode 13 is present. The device isfabricated on a substrate 15, which may be any insulating material, forexample silica based, or any conducting material, for example silicon,provided that there is an insulating layer 17 between the saidconducting substrate and the said electrodes 11 and 12 and nanotubes 14.A junction 16 between the nanotubes 14 and at least one of theelectrodes 11, 12 acts as a sensing element. Specificity for particularmolecules in a fluid analyte is controlled by the choice of materialused for at least one of the electrodes 11, 12. The nanotubes 14 may besingle-walled carbon nanotubes (SWNT), having a diameter of between 1 to2 nm. Further, the nanotubes 14 may comprise a single tube, multipletubes or a network of interconnected tubes. In some embodiments, thenanotubes 14 may be multi-walled nanotubes (MWNT). The nanotubes 14 maybe semiconducting depending on the chirality of the nanotube. At leastone of the electrodes 11 and 12 may be of metal or an alloy. Forexample, the electrodes 11, 12 may be of Ti, Pd, Au. It should be notedthat while the present invention is described using carbon basednanotubes this is intended to be non-limiting. Thus, nanotubes made ofmaterials other than carbon, e.g., silicon nanowires and inorganicnanorods, may also be used.

[0031] The fabrication of carbon nanotube sensors may be based onnanotubes grown from an unpatterned catalyst 21 over a substrate 15, asillustrated in FIG. 2A. Alternatively the fabrication may be based on apatterned catalyst 22 over a substrate 15 as illustrated in FIG. 2B.Catalyst sites 21 or 22 on a substrate 15 lead to the growth ofnanotubes from these sites. Following either unpatterned or patternedcatalyst growth, optical lithography is then used for placing metalelectrodes 11 and 12 to connect to the nanotubes in a controlled manner,as shown in FIG. 3A for the unpatterned catalyst and in FIG. 3B for thepatterned catalyst. One procedure includes the following steps:

[0032] (1) catalytic particles are attached to the entire surface of thesubstrate 15 for unpatterned growth (FIG. 3A) or patterned on asubstrate to form catalyst arrays for patterned growth (FIG. 3B). Thepatterning is done by a shadow mask or a photolithography technique.

[0033] (2) SWNTs are then grown by chemical vapor deposition from thecatalyst sites.

[0034] (3) metal electrodes 11 and 12 are then placed onto SWNTs grownfrom the catalyst patterns by an optical lithography, metallization andliftoff procedure. In the case of patterned growth, this lithographystep may involve optical alignment in registry with the catalystpatterns (See FIG. 3B). Growth by CVD combined with the microfabricationapproach is a scalable approach to produce nanotube electronic devicesincluding sensors.

[0035] The resistance of a nanotube device comprises channel resistanceand contact resistance. Channel resistance is the resistance from oneend of the nanotube 14 to the other, whereas contact resistance is theresistance between the metal contacts 11, 12, and the nanotube 14.Contact resistance is defined by the Schottky barrier (work function)that forms at the metal-nanotube junction 16. A change in the workfunction of the metal can change the contact resistance dramatically.The work function of a particular metal may be changed upon exposure tospecific chemicals. By using this principle a nanotube-based sensor canbe tailored to be selective to specific molecules in fluids. In oneembodiment of the invention, the work function change of at least one ofthe electrodes 11 and 12 of a nanotube device is used for sensingmolecules in fluids as can be seen from the following examples.

[0036] Working examples for the sensing of H₂ with Pd electrodes andsensing of H₂S with Au electrodes are shown in Examples 1 and 2 below.It should be noted that while Pd and Au electrodes were used in theexamples, Pd alloys such as PdNi and gold alloys such as AuPd may alsobe used.

[0037] In the Examples 1 and 2 that follow, a nanotube electronic sensorwas fabricated by patterned growth of SWNTs on full 4-inch SiO₂/Siwafers. A SiO₂/Si wafer was first fabricated to get the alignment marksby standard photolithography with 1 μm Shipley 3612 as the photoresist.Then the patterned catalyst islands were fabricated with a quartz maskand dry etching on PMMA and Shipley 3612 coated silicon wafer.Afterwards a thin catalyst layer of suspension consisting of 15 mlmethanol, 0.05 mmol Fe(NO₃)₃9H₂O, 0.015 mmol MoO₂(acac)₂, and 15 mgDegussa alumina nanoparticles was coated on the patterned substrate.After lifting off with acetone, single-walled carbon nanotubes weregrown at 900° C. for 7 min with 3.375 SLM CH₄ and 0.281 SLM H₂. Aftertube growth, standard photolithography was applied again for metalelectrodes with alignment marks. Ti, Pd and Au have been used as theelectrodes materials, with a highly doped Si wafer used as a backgate.The thickness of the thermal oxide layer of SiO₂ is about 100-1000 nm.Cleaning procedures were applied by heating the devices in acetone at50° C. for 1 hour and then on a hot plate at 300° C. for 1 hour toprovide a clean surface after lift-off.

EXAMPLE 1

[0038] For sensing H₂, devices were fabricated as described. However,the nanotubes were not coated with nanoparticles of Pd as in prior artnanotube and nanowire sensors, but instead the metal contacts 11 and 12in this case were prepared by depositing 50 nm Pd using electron-beamevaporation. Devices were diced and then wire-bonded to chip-carriersfor gas sensing experiments. When the device was exposed to 2% H₂ inair, a rapid current decrease was observed, as shown in FIG. 4A. Thedevice quickly recovered to baseline current after purging of H₂ gas andexposing to air for about 5 min. FIG. 4A shows this procedure repeated 4times. The adsorbed hydrogen gas changed the work function of the Pdelectrode 11, 12, giving rise to the rapid current decrease. Uponexposure to air, the dissolved atomic hydrogen in Pd electrodes reactedwith oxygen in air resulting in the recovery of H₂ sensor. Heating thesensor at a moderate temperature shortened the recovery time as shown inFIG. 4B. As a control, a device with Ti electrodes connected tonanotubes did not show a response upon exposure to 2% H₂.

EXAMPLE 2

[0039] For sensing of H₂S, devices were fabricated as described, andinstead of depositing nanoparticles of gold on nanotubes 14 as would bedone in prior art sensors, the metal contacts in this case were preparedby depositing 25 nm gold using electron-beam evaporation. FIG. 5 showsthe response of the device to exposure of 20 ppm H₂S in air, carried outtwice. When the device was exposed to 20 ppm H₂S, a rapid currentdecrease was observed. The device quickly recovered to baseline afterpurging of H₂S gas and exposing to air. To confirm that the goldelectrodes had functioned as the H₂S sensing element, a device with Tielectrodes connected to nanotubes did not show a response upon exposureto 20 ppm H₂S.

[0040]FIGS. 6A and 6B show the sensitivity dependence of a nanotubedevice from Example 2 on different H₂ concentrations without applicationof a gate voltage (FIG. 6A) and with −5 V gate voltage on (FIG. 6B). Thesensitivity is defined as the conductance difference before and aftersensing divided by the base conductance. It was demonstrated that thelinearity and sensitivity of a nanotube device can be improved byapplying −5 V gate voltage during sensing. Negative gate can decreasethe contact resistance and result in a wider linear region for sensing.With −5 V gating a linear response on H₂ concentration up to 300 ppm wasobtained, as shown in FIG. 6B.

[0041] For the following examples 3 and 4, an iron-based catalyst wasdeposited on wafers homogenously. The Fe-containing nanoparticleformation was achieved by immersing the SiO₂/Si substrate into ascintillation vial containing 10 mL of water and 10 uL of 10 mM FeCl₃6H₂O (aq), followed by immediate addition of 100 uL of 40 mM NH₂OHHCl-(aq) into the vial. After a few seconds stirring, the substrate wasallowed to soak in the solution for a certain period of time (10 s to 5min) before being taken out of the solution, rinsed consecutively withwater, acetone, and isopropyl alcohol, and dried. After the liquid phasedeposition process, the substrate was calcined in air at 800 C for 5min. Nanotube growth was performed with chemical vapor deposition of CH₄and H₂ in a 6 inch quartz tube at 900 C degree. Mechanical shadow maskswere used for metal pad deposition. Metal deposition of Pd was performedby DC sputtering with a power of 50 W and a pressure of 5×10⁻³ torr. Thethickness of the metal was controlled to be 20 nm by sputtering time.Alternatively, instead of mechanical shadow masks, deep UV lithographywas also used to fabricate devices, and polymethylmetharcylate (PMMA)was used as resist. After deep UV exposure and development, Au/Pd metalswere used as electrodes. Firstly 20 nm Pd was sputtered with a power of50 W and a pressure of 5×10⁻³ torr, subsequently 20 nm Au was sputteredwith the same power and pressure. Acetone was used for lift-off. Thewafer was diced to get chips for testing. Afterwards chips were cleanedin Ar atmosphere at 200 C degree for 30 min.

EXAMPLE 3

[0042] For sensing of streptavidin, devices were fabricated as describedabove. To test the device for streptavidin, 1 mM phosphate solution wasused as buffer, and 1 nM to 1 μM streptavidin in 1 mM phosphate solventwas introduced sequentially, with a constant bias voltage of 10 mV beingapplied between the two electrodes. During this time, the current wasmonitored with Keithley 237. The result was shown in FIG. 7. Ameasurable resistance change was observed when 1 nM streptavidin wasintroduced. The resistance change increases with the streptavidinconcentration. After sensing 1 μM streptavidin, the devices were imagedwith an atomic force microscope. The substrate and Au/Pd electrodes werefound to be coated with streptavidin. Control experiments found thatnanotubes are not sensitive to streptavidin after passivation of Au/Pdelectrodes with protein-resistant self-assembled monolayers ofmethoxy-(polyethylene glycol)-thiol. AFM images of a Au/Pd electrodebefore sensing and after sensing streptavidin are shown in FIG. 8A andFIG. 8B, respectively. After sensing, the electrode was coated with asub-monolayer of streptavidin, which is consistent with the results ofsurface plasmon resonance (J.-J. Gau et al, Biosensors & Bioelectronics16 (2001), 745) which indicate a sub-monolayer coverage of streptavidin.The absorbed streptavidin introduced dipoles which change the workfunction of the electrodes, therefore changing the contact resistance,and finally the conductance of the device.

EXAMPLE 4

[0043] For sensing of streptavidin in another way, devices werefabricated as described above. The metal contacts in this case weremodified by adding biotin. The procedure is illustrated in FIG. 9. Thesource and drain electrodes 91 and 92 of an unpatterned device with gap93 and nanotubes 94 were modified with a biotinylated self-assembledmonolayer (SAM) 95 by incubating the device with a 1 mM ethanol solutionof 2-(biotinamido-ethylamido)-3,3′-dithioldipropionic acidN-hydroxysuccinimide ester (biotin-disulfide) for 2 hours. The deviceswere rinsed with ethanol and dried with argon. Poly-dimethylsiloxane(PDMS) stamps were used to confine the liquid for sensing. 1 mMphosphate with a pH value of 7.2 was used as the buffer and solvent forstreptavidin 96 of different concentrations. A constant bias voltage of10 mV was applied between the two electrodes for real time sensingmeasurements. 10 μL 1 mM sodium phosphate was added as a buffer beforeintroducing streptavidin, and then 5 μL streptavidin with differentconcentrations was introduced. FIG. 10 shows a real-time currentmeasurement as streptavidin with different concentrations was added. 333nM strepavidin induced an obvious current decrease, labeled as 1 micromolar, before dilution. Immobilization of biotin-sulfide on the surfaceintroduced surface dipoles, and after binding with streptavidin thesedipoles vary, and hence induce a work function change of the Au/Pdelectrodes. Charge transfer between the carbon nanotube and theelectrode occurred because of the work function change. The chargetransfer results in a contact resistance change. Experimentally it hasbeen found that nanotubes are ballistic in electrical transport,indicating that the channel resistance is negligible. However forsilicon nanowires, previous studies indicate that diffusive (channel)conduction dominates. Therefore more sensitive sensors can be fabricatedwith carbon nanotubes based on the work function change of electrodes.

[0044] The selectivity of the sensors may be improved by havingnanotubes or nanowires 14 uniformly coated with protective layers, suchas polymers, that will block other molecules from contact with nanotubesor nanowires. The device will still function because the electrodes andthe junction between electrodes 11, 12 and nanotubes or nanowires 14will remain uncoated. In one embodiment, a gate voltage may be appliedto the gate electrode 13 to alter the Schottky barrier at the junctionthereby to change the sensitivity of the sensor. The gate voltage mayalso be applied to change the recovery time of the sensor. Anotheradvantage of this approach is better ability to produce sensing deviceswith wider dynamic sensing range, because the effective work function ofalloy in the electrode 11, 12 can be continuously adjusted by differentcompositions of alloys.

[0045] By using Pd alloy-based thin film electrodes 11, 12, the Pdbecomes a stable material, thereby resulting in a higher longevity forthe sensors of the present invention. The sensors of the presentinvention also exhibit higher sensitivity, because instead of using acharge transfer as a mechanism of molecule detection, the sensors of thepresent invention employ a contact barrier between the electrodes of thesensor and the nanotube(s) in which case electrical current isexponentially dependent on the barrier. Another advantage of the sensorsof the present invention is that they can be fabricated by a simplifiedprocess, because production of thin-film Pd alloys is a well understoodand widely established industrial process. This will result in a lowermanufacturing cost and better reproducibility for the servicing devicesof the present invention.

What is claimed is:
 1. A method for sensing specific molecules, themethod comprising: forming a nanoelement structure; and forming twospaced apart electrodes in contact with the nanoelement structure,wherein at least one of the electrodes is capable of functioning as asensing element to sense the specific molecules.
 2. The method of claim1, further comprising coating the electrode with a material to enhancethe sensitivity of the electrode to the specific molecules.
 3. Themethod of claim 1, wherein the nanoelement structure comprises elementsselected from the group consisting of a hollow nanotube and a solidnanowire.
 4. A method for sensing specific molecules, the methodcomprising: forming a nanoelement structure; forming two electrodes incontact with the nanoelement structure; and treating at least one of thetwo electrodes with a material to enable the electrode to function as asensor for the specific molecules
 5. The method of claim 4, wherein atleast one of the two electrodes comprises a material selected from thegroup consisting of Pd, PdNi, Au, and AuPd.
 6. The method of claim 4,wherein the nanoelement structure comprises elements selected from thegroup consisting of a hollow nanotube, and a solid nanowire.
 7. A devicefor sensing specific molecules, the device comprising: a nanostructure;and two electrodes connected by the nanostructure, wherein at least oneelectrode and a junction between the electrode and the nanostructuredefines a sensing element for the specific molecules.
 8. The device ofclaim 7, wherein the nanostructure comprises at least one nanoelementselected from the group consisting of a hollow nanotube and a solidnanowire.
 9. The device of claim 8, wherein the nanostructure comprisesa carbon nanotube.
 10. The device of claim 7, wherein at least oneelectrode that defines the sensing element is coated with a material tosensitize the electrode to the specific molecules.
 11. The device ofclaim 7, wherein the material comprises palladium.
 12. The device ofclaim 11, wherein the specific molecules comprise H₂ molecules.
 13. Thedevice of claim 11, wherein the device is for sensing at least onehydride gas.
 14. The device of claim 11, wherein the operatingtemperature for the device is from room temperature to 120° C.
 15. Thedevice of claim 7, wherein at least one of the electrodes comprisesgold.
 16. The device of claim 15, wherein the specific moleculescomprise H₂S molecules.
 17. The device of claim 15, wherein theoperating temperature for the device is from room temperature to 250° C.18. The device of claim 7, wherein at least one of the two electrodecomprises palladium and gold.
 19. The device of claim 16, wherein thespecific molecules comprise bio-molecules.
 20. The device of claim 16,wherein the specific molecules comprise streptavidin molecules.
 21. Thedevice of claim 18, wherein at least one of the two electrodes isimmobilized with a chemical that comprises biotin.
 22. The device ofclaim 21, wherein the specific molecules comprise streptavidinmolecules.
 23. A device for sensing fluids, the device comprising: atleast one nanoelement; a first electrode and a second electrodeconnected by the at least one nanoelement; a third gate electrodedisposed between the first and second electrode, wherein at least one ofthe first and second electrodes and a junction between the electrode andthe at least one nanoelement defines a sensing element for the specificmolecules; and wherein a gate voltage applied to the third gateelectrode changes the Schottky barrier at the junction.
 24. The deviceof claim 23, wherein the nanoelement is selected from the groupconsisting of a hollow nanotube and a solid nanowire.
 25. The device ofclaim 23, wherein the nanoelement comprises a carbon nanotube.
 26. Thedevice of claim 23, wherein at least one of the first and secondelectrodes comprises palladium.
 27. The device of claim 26, wherein thespecific molecules comprise H₂ molecules.
 28. The device of claim 26,wherein the specific molecules comprise at least one hydride gasmolecule.
 29. The device of claim 23, wherein at least one of the firstand second electrodes comprises gold.
 30. The device of claim 29,wherein the specific molecules comprise H₂S molecules.
 31. The device ofclaim 29, wherein the specific molecules comprise a bio-molecule. 32.The device of claim 23, wherein the third gate electrode comprisessilicon.
 33. The device of claim 23, wherein the third gate electrodecomprises a metal.
 34. The device of claim 23, wherein at least one ofthe first and second electrodes comprises palladium and gold.
 35. Thedevice of claim 34, wherein the specific molecules comprise abio-molecule.
 36. The device of claim 34, wherein the specific moleculescomprise streptavidin molecules.
 37. The device of claim 34, wherein atleast one of the first and second electrodes is immobilized with achemical that comprises biotin.
 38. The device of claim 37, wherein thespecific molecules comprise streptavidin molecules.
 39. A field-effecttransistor device, comprising: at least one nanoelement; and a first anda second electrode connected by the or each nanoelement, wherein atleast one of the first and second electrodes includes palladium.
 40. Thetransistor device of claim 39, wherein the electrode that includespalladium includes an alloy of palladium.